In numerous disorders in the area of cardiology, for example in a case of myocardial infarction or in cases of cardiac arrhythmia, the propagation of electrical signals in the heart is altered. This results in a change in the electric field of the heart, the sum vector of which is evident in changes in the electric potentials on the body surface of a patient.
In an electrocardiogram (ECG), the electric potentials and/or the changes in the electric potentials at the body surface of the patient are captured, in order to draw conclusions therefrom as to the propagation of electric excitation in the heart and/or as to the electric field of the heart. The changes of potential are represented over time as curves in order in this way to enable a doctor subsequently to diagnose disorders.
In a conventional ECG, assessment of cardiac impulse conduction is restricted, however, as the electrodes even in a 12-channel ECG are not arranged in all planes, so that propagations of the electric field which have a vector perpendicular to the planes captured are not captured. This problem can be partially solved by increasing the number of electrodes. As a result of this, however, diagnosis becomes increasingly difficult as the number of curves is very high and these are ultimately difficult to interpret so that highly trained specialists are required to assess them.
Rather than recording the changes of potential at the body surface of the patient as individual curves, it is therefore advantageous actually to record the propagation of impulse conduction in the heart, i.e. the corresponding sum vector itself. It would in this way be significantly easier in a subsequent diagnosis to detect cardiac disorders and to plan a treatment.
A representation of this type is referred to as a “vector cardiogram”, and it has been possible for it to be determined in the research field, for example, in the isolated beating heart. In a living patient, the reconstruction of such a vector cardiogram is possible only with very great difficulty as the currently existing solutions are associated with considerable costs.
For example, DD 284 594 shows a device for deriving cardiac potentials, in which the electrodes are brought into position by means of mechanical positioning aids. The position of these positioning aids is then measured and this information utilized.
The reason why the currently existing methods for the reconstruction of vector cardiograms are very costly and of limited practicability, is that, in order to reconstruct the propagation of excitation of the heart on the basis of the measured potentials, the precise position of the electrodes used and the anatomy, i.e. in particular the shape of the heart, have to be known.
The publication US 2004/0082870 A1 relates to systems and methods for determining a surface geometry of an object, providing for the determination of a first projection matrix based upon a first imaging device, the determination of a second projection matrix based upon a second imaging device, the recording of at least one first two-dimensional image of the object using the first imaging device and the recording of at least one second two-dimensional image of the object using the second imaging device and the determination of a contour of the object in the first two-dimensional image and the second two-dimensional image. Taking the at least two contours, the first projection matrix and the second projection matrix as a basis, the aim is to reconstruct three-dimensional data which relates to the surface of the object, which may be the heart of a patient. Where a vest with electrodes is used, the torso geometry and thereupon the positions of the electrodes can be determined from image data. In addition, the electric potentials at the body surface can be measured with the aid of the electrodes of such a vest.